1. Field of the Invention
The present invention relates to an exercise therapy device such as an ergometer and a treadmill, and more particularly, to a control apparatus and method for an exercise therapy device for controlling an exercise load to be applied to an exerciser so that a measured value of the exerciser's physiological response to exercise, such as his/her heart rate and pulse rate, approaches a preset target value.
2. Description of the Related Art
In a related-art exercise therapy device typified by a cycle ergometer, a rotation speed of pedals is measured with use of an encoder mounted to the device and further, a load torque applied to the pedals is measured based on a current value flowing through a load motor. The load motor is then controlled so that the thus acquired measured value of the rotation speed or load torque of the pedals approaches a target value of the rotation speed or load torque of the pedals (see, for example, Japanese Patent Application Laid-open No. Hei 10-179660).
There is also known an exercise therapy device for controlling the exercise load in accordance with a heart rate or a pulse rate, which is the exerciser's physiological response to exercise (hereinafter referred to as “exercise physiological response”). In such exercise therapy device, the rotation speed and load torque of the pedals are controlled so that a measured value of the exerciser's exercise physiological response reaches a target value of the exercise physiological response, which is preset in the exercise therapy device, to thereby adjust an exercise load to be applied to the exerciser (see, for example, Japanese Patent Application Laid-open No. Sho 63-35254).
In addition to the cycle ergometer, there is further known an exercise therapy device using, for example, a treadmill as such exercise therapy device for controlling the exercise load to be applied to the exerciser in accordance with the exerciser's exercise physiological response (see, for example, Japanese Patent Application Laid-open No. 2002-177413).
However, the related arts have the following problem.
In the exercise therapy device such as an ergometer and a treadmill, a delayed response time passing until the exerciser's heart rate follows a change of the exercise load to reach a state after the change differs depending on, for example, states of the exerciser's sympathetic nerves and parasympathetic nerves and the exerciser's response time constant including a dead time and a first-order lag as the exercise physiological response. In particular, the response time constant of the exercise physiological response of a patient with cardiac disease is known to become larger than that of a healthy person as the level of severity of the patient's heart failure becomes larger. For example, New York Heart Association (NYHA) classifies the level of severity of the heart failure as the NYHA classes, and a patient having the NYHA class associated with a higher level of severity has a larger response time constant of the heart rate.
However, in the related-art exercise therapy devices, such response time constant of the exerciser's heart rate has not been taken into consideration. Therefore, in a case of the exerciser who has a large response time constant such as a patient with cardiac disease, a deviation between the target value of the heart rate and the measured value thereof is undesirably larger than that of a healthy person. As a result, an amount of the exercise load increased by control of the exercise load becomes larger, and hence the exercise load is undesirably liable to exceed an upper limit value of the exercise load allowable for the exerciser or the exercise therapy device, which has been a problem of the related-art exercise therapy devices.